The present invention generally relates to data base management system extending structures, and more particularly to a data base management system extending structure involving pre-processing of a data model in a data base management system and extending and pre-compiling of a data base language for realizing an external view of a link-oriented data model.
The conventional relational data base control system offers data transparency, data independence, and non-procedurality of its operations. However, a generation of an optimum access path is complex and there is a disadvantage in that the access efficiency is low because of a value-based representation of relationships in a relational data model.
Accordingly, a link-oriented data base managment system based on a link-oriented data model employing a link-oriented representation of relationships has been proposed to improve the access efficiency and provide an optimum access path. The link-oriented data model represents the entities as record-types and the relationships as link-types. The link-oriented data base management system also enables the user to positively handle the relationships between objective data within the data base, thereby making it possible to convert an entity-relationship of the actual world into an internal schema.
A link-oriented data base management system called a GraphBase is commercially available. The GraphBase is based on a graph data model (GDM). The GDM is an extension of the relational data model and incorporates the structure of directed graphs, where anode corresponds to a record occurrence and an edge corresponds to a link occurrence.
Although the link-oriented data base management system enables representation of multiple corresponding relationships (many-to-many relationships) between two entities, there is a disadvantage in that it is impossible to positively handle attribute information which is inherently and directly determined by the relationships.
On the other hand, the conventional relational data model must represent both the entity and the relationship in tables, and a technique peculiar thereto is required to make a description using the relational data mode. Generally, such a description becomes extremely complex and it is virtually impossible to make a natural description.